Vulcanization of rubber



Patented Mar. 14, 1933 units s'rArss CLYDE CCLEMAN, or PASSAIC, Nnw annsny, ASSIGNOR 'ro 'rnn NAUGATUCK CHEMICAL. COMPANY, or NAUGAT'UCK, CONNECTICUT, A ConPonA'rIoN or CONNECTICUT VULOANIZATION F RUBBER No Drawing.

This invention relates to the preparation of a new class of chemical compounds and to the resulting products, and to the employ: ment of these compounds in the vulcanization of rubber and other vulcanizable materials.

It has been found that the reaction products prepared by interacting a mercaptothiazole, a primary aromatic amine and formaldehyde under conditions precluding the elimination of hydrogen sulphide form-a new and valuable class of vulcanization accelerators. The following probable general formula is assigned to the new accelerators: R SCH NHR wherein R is a substituted or unsubstituted aryl group and R is a thiazyl group, for example a benzothiazyl group.

Compounds comprising a benzothiazyl group are numbered for the purposes of this invention as indicated in the following structure:

Among the mercaptothiazoles which may be reacted with the primary aromatic, amine and formaldehyde are the mercaptoarylthiazoles, such as Q-mercaptobenzothiazole, and homologues and substitution products thereof, for instance Q-mercaptotoluthiazole sometimes referred to as Q-mercantotol lthiazole), 2-mercapto-6-nitrobenzothiazole, 2-mercapto-5-nitrobenzothiazole, Q-mercapto-6-chlorobenzothiazole, 2-mercapto-6-etl1- oxybcnzothiazolo, 2 meroapto chlorobenzothiazole.

The new compounds may be prepared as illustrated in the followin examples: 7

Example A.-Reaction product of mercaptobenzothiazole, formaldehyde, and ortho-toluidine having the probable formula:

Application filed September 55,1931. Serial No. 561,503.

thoroughly agitated, the :mercaptobenzothiazole remaining largely in suspension. An aqueous solution of formaldehyde of about 38l0 strength containing 4 moles of fornialdehyde is then added with agitation, and

cooling if necessary. A reaction between the ortho-toluidine, formaldehyde, and the mercaptobenzothiazole takes place quickly at room temperature, and the new productseparates as a fine nearly white crystalline solid of a high degree of purity. The product is recovered from the supernatant liquid and freed ofsolvent. The melting point is about 14514l6 C. The amount recovered in this way is about 960 grams (about 83% of theo- 107 grams (one mole) of para-toluidine are dissolved in about 500 cc. of alcohol, andl67 grams of mercaptobenzothiazole are then 85 added and the mixture is thoroughly agitated. An aqueous solution of 88l0% of, formaldehyde containing one'mole of formaldeliyde is then added. The new product, which" is the reaction product of para-tolui'dine, formaldehyde, and mercaptobenzothiazol'e, separates from the alcohol as a yellowish white crystalline solid, and isrecovered as in* the previous example. The product thus 0b tained weighs about 195 grams. I The melting point is about 107 C. which is raised to 110111 C. by recrystallizing the product from alcohol. About 90 grams of the product remain in solution'and may be recovered by any suitable means therefrom; it is identical With the first fraction isolated.

Example C.lteaction product of mercap tobenzothiazole, formaldehyde and aniline having the probable formula 46.5 grams of aniline (0.5 mole) and 83.5 grams of mercaptobenzothiazole (0.5 mole) are added to 800 cc. of alcohol; the mercaptobenzothiazole remains largely in suspension while the aniline is completely dissolved,

no reaction occurring between the two materials. 7 Then an amount of formaldehyde solution of about 38% strength containing 15 grams (0.5 mole) of formaldehyde is added and the mixture is agitated. The temperature of the reaction mixture rises to about 80 C. As the reaction proceeds, the contents of the flask begin to assume a lighter color I and after about 1015 minutes the reaction is lCH3 12.1 grams of para xylidine 0.1 mole) are dissolved in about 100 cc. of alcohol, and 16.7 grams I (0.1 mole) of mercaptobenzothiazole are added. The mixture is thoroughly agitated, and an amount of formaldehyde solution of about 38% strength containing 3 grams (0.1 mole) of formaldehyde is added. To hasten the reaction the temperature is raised to about 30C. When substantially all of the mercaptobenzothiazole has reacted with the p-xylidine and formaldehyde, the resulting product, after a short time, begins to separate from the solution as a, white, crystalline solid. lVhen the crystallization .is complete the reaction product is recovered in any suitable manner. It melts at about 119-120 C. The yield thus obtained is 27.5

new compounds by the reaction of formalde-v hyde and mer captobenzothiazoles with any primary aromatic amine. It is preferable to employ as the reaction medium an organic solvent in which the reaction product is not too soluble. For this purpose alcohol, benzene, toluene, and xylene are suitable. In the case of the reaction using 2, 5-dichlor0 aniline or alpha naphthylamine it ismore desirable to employ benzene, toluene, or xylene, xylene being preferable on account of the lesser solubility of the products therein and the corre 'spondingly greater ease of recovery of the products.

Other modifications of the process may be employed as illustrated in the fol-lowing examples: V Example E.It has been found that product identical with that of Example C may be prepared in the following manneri 93 grams of aniline, 167 grams of mercaptobenzothiazole and cc of 40% formaldehyde solution are mixed in a vessel with a powerful stirring apparatus, and heated to about 80 C. The contents of the vessel become fluid for a time, and as the reaction proceeds, gradually harden to a light bufi' hOmO- geneous mass having melting point of Example F.The same product may also be prepared in the following method:

grams of anhydro-formaldehyde aniline, prepared by the reaction between formaldehyde and aniline in known manner, and 167 grams of mercaptobenzothiazole are melted together with stirring. On heating for a time at about 80 C, the whole mass sets to a homogeneous solid melting at 111112 C.

Example G.The solvents which may be used in the process of Example G- are the same as those which may be used in the process of Examples A, B, C, and D.

105 grams of 1 methylene aniline are dissolved in 100 cc of benzol; 167 grams of mercaptobenzothiazole are added, and the solution warmed to 5060 C. The mercaptobenzothiazole goes into solution, and soon the product of the reaction crystallizes from the solvent. It melts at 111-112 C. and is identical with theproduct of Example C. a

T he -method illustrated by the process'of Example E is especially suited tomake con densations with such bases as aniline, o-toluidine and other fluid or low melting bases. The method illustrated by the process of Examples F and'G is applicable in the case of those primary aromatic amines which are capable of formng with formaldehyde the" corresponding isolable tertiary methylene Reaction product of- Color M. P.

Degrees 1 centi grade Alfietcaptobenzothiazole formaldehyde and ani- Bufi. 111-112 1116 Mercaptobenzothiazole formaldehyde and Butt 146 o-toluidine l lercaptobenzothiazole formaldehyde and Bufi 110-111 p-toluidine Mercaptobenzothiazole formaldehyde and Buff 120 p-xylidine Mercaptobenzothiazole formaldehyde and Bufi. 156

o-chlor aniline Mercaptobenzothiazole formaldehyde and Bufl'. 125 alpha naphthylamine Mercaptobenzothiazole formaldehyde and Bufi 161-162 p-chlor aniline 5-chloro mercaptobenzothlazole formaldehyde Yellowlsh 120 and aniline whlte Mercaptobenzothiazole formaldehyde and Light buff. 138

B-naphthylamine 5-nitro mercaptobenzothiazole formaldehyde Yellowish 134 and o-toluidine orange 5-nitro mercaptobenzothiazole formaldehyde Greenlsh 115 and b-naphthylamine brown 5-nitro mercaptobenzothiazole formaldehyde Reddlsh 119l20 and aniline prange Mereaptobenzothiazole formaldehyde and h1te.. 98

- p-anisidine Mercaptobenzothiazole formaldehyde and 2-5 Buff 172 dichlor aniline '35 Para-formaldehyde or other polymerlc forms of formaldehyde may be used in the process of the invention 1n place of formalde- F v 40 hy le.

The moderate temperatures employed in the processes of the invention cause the reactions to take place without the elimination of any sulphur-containing substances such as hydrogen sulphide; water is eliminated durthe amine. All of the reaction products which fall within the scope of the invention are definite crystalline compounds.

The liability of the hydrogen atom of the mercapto group contained in mercaptothiazoles is well known, as is the tendency of such unsaturated groups as the C=N group, present in methylene aryl-imides, to become saturated by the opening up of the double bond and the addition thereto oftwo. monovalent elements or groups, especially when one of the said elements or 'roups available is labile hydrogen atom. Accordingly, the reactions of the present process are considered to proceed by the additionof the mercaptothiazole to the C=N group of a methylene.

aryl-imide, the methylene aryl-imide (or tertiary methylene base) being present either by direct addition to the reaction mixture as- Examples of products which fall within the ing the condensation of formaldehyde with in Examples F and G, or by reason of its momentary formation in situ in the reaction mixtureas in Examples-A'to E, inclusive. The labile hydrogen atom of the mercapto group" wanders tothenitrogen of ;the methylene imide group, and the residue of the mercaptothiazole molecule becomes attached, through the mercapto sulphur Iatom, tothe carbon atom ofthe methylene group. These 7 changes may be illustrated, by writing the equation for the reaction in the following manner: f -1"' wherein and R are as defined above. The Y dotted lines indicate the respective points of 5 attachment of theH atom and of the R S grouping to the C=N group. The equation also shows that the reaction takes place without the elimination of any simpler sulphurcontaining substances. I All of the elements of the methylene imide and of the mercapto thiazole are seen to be present in the molecule of the final product; ill; will also be noted that the trivalent nitrogen atom contained in the methylene aryl-imide remains trivalcut in the reaction product. l J

In view of the preceding, it is to be understood that the expression reaction product as used in the'claims means the product of a reaction in which no hydrogen sulphide is eliminated. 1

In' view of the fact that the polymeric forms of methylene aryl-imides behave chemically as if they were the simple monomers having the formula R N=CH' it is obvious that the polymeric forms of said bases are equivalentto the corresponding monomers for the purposes of this invention, and it is to be understoodthat the expression methylene aryl-imide asused in the claims includes both'the' monomeric andthe' polymeric forms of said bases,

The new materialsofthis invention may be used in the vulcanization ofvarious rubber compounds. For the purpose o f'illus trating the invention, the following examples are given, without limiting it thereto. Compoun-dsof the following compositions were used:

, a r Y 7 I Parts by weight Smoked sheets "100 1 00 Carbon black 42 142 j Sulphur 3. 25 3.25 Zinc oxide 10 1 10 Stearic acid; 3.25 3.25 Pine tar. 3.5 3.5 Antioxidant 1. .25; 1.25 New'accelerator 0.8 f Mercaptobenzothiazoleii -11. 125

'gensiglal Per cent s reng conga- Accelerator Amount Time in Pres (lbstper Vtmn i minmm Sure sq. 111.): biea Product of Example 0. 8 .45 4301 690 A. 0. 8 6O 30# 4433 700 0.8- I 75 30#. V 4543 680 0.8 90 30# 4393 V 620 Product of Example 0. 8 30# g 4404 710 C. 08 30# 4277 660 0. 8 75 30# 4670 p 670 0.8 p 90 30% 4414 630 Merceptobenzothi 1. 125 45 30# 4527 690 azole. 1. 125 7 60 30# 4463 650 1.125 75 30# p 4453 640 1. 125 90 30#' 4293 610 Product of Example 0. 8- 45 30# 3971 710 B. 0. 8 60 30# 3925 690 0.8 75 30#, 3912 660 0.8 9O 30# 4069 640 Mercaptobenzothi 1. 125 45 30# 4014 690 azole. l. 125 60 v 30# 4213 670 1; 125 75 30# 4180 650 1.125 90 30# 4129 610 As concerns their use in rubber, the new chemicalsare not to be restricted to the par- 'ticular method ofpreparingthem as set forth 1n detail above, and the claims are to be con-.

- the rubber at any time prior to theactual n the preparation of inner tubes, tires, thread,

hose, dippedgoods, mechanical'goods, latex orarti'cles made from latex, etc.

With the detailed description given above, it will be obvious that modifications will suggest themselves without departing from the principle of theinvention, and it is not desired to limit the invention otherwise than as set forth in the appended claims.

Having thus described my invent-ion, what ent is Y r r 1. A process of treating rubber which comprises vulcanizing rubber inthe presence of the reaction product formed by thereaction of equi-molecular proportions of amor- -I claim and desire to protect by- Letters Patcaptobenzothia-zole, formaldehyde, and a primary aromatic amine.

2. A process of treating rubber which comprises vulcanizing rubber in the presence of the reaction product formed by the reac tion of equi-molecular proportions of mercaptobenzothiazole, formaldehyde, and av molecular proportions of a mercaptobenzo- .thiazole and a methylene aryl-imide having the formula R'N=CH .in which R is an aryl group. v p

. 5. Aprocess of treating rubber'which comprises incorporating in rubber sulphur and the reaction product formed by the reaction of equi-molecular proportions of mercaptobenzothiazole and a methylene aryl-imide having theformula RL T=CH in which R is an aryl'group. I

6. A process of producing vulcanized rubber which comprises vulcanizing rubber containing sulphur in the presence of the reaction product formed by the reaction of equimolecular proportions of mercaptobenzothiazole and a methylene aryl-imide having the formula R-N=CH in which R is an aryl group. I

7. A process of producing vulcanized rubber which comprises vulcanizing rubber containing sulphur in the presence of the reaction product formed by the reaction of equimolecular proportions of a mercaptobenzothiazole and methylene aniline.

8. A process of producing vulcanized rubber which comprises vulcanizing rubber containing sulphur in the presence of the reaction product formed by the reaction of equimolecular proportions of a mercaptobenzo thiazole and 'a methylene toluidine.

9. A process of producing vulcanized rubber which comprises vulcanizing rubber containing sulphur in the presence of the'reaction product formed by the reaction of equimolecular proportions of a mercaptobenzothiazoleand methylene o-toluidine.

10. A process of producing vulcanized rubber which comprises vulcanizing rubber con taining sulphur in the presence of the'r'eaction product formed by the reaction of equimolecular proportions ofa mercaptobenzothiazole and methylene p-toluidine.

11. A process of producing vulcanized rubber which comprises vulcanizingrubber in; the presence of the reaction product formed by the reaction of equi-molecular mercaptobenzothiazole, formaldehyde, and

aniline.

14. A process of producing vulcanized rubber which comprises vulcanizing rubber containing a vulcanizing agent in the presence of the reaction product formed by the reaction of equi-molecular proportions of mercaptobenzothiazole, formaldehyde, and a toluidine.

15. A process of producing vulcanized rubber which comprises vulcanizing rubber containing a vulcanizing agent in the presence of the reaction product formed by the reaction of equi-molecular proportions of mercaptobenzothiazole, formaldehyde, and o-toluidine.

16. A process of producing vulcanized 24. A vulcanized rubber product resulting from the process as set forth in claim 8. V 25. A vulcanized rubber product resulting from the process as set forth in cl aim 9. Y

26. A vulcanized rubber product resulting from the process as set forth in claim 11.

27. A vulcanized rubber product resulting from the process as set forth-in claim 12. 1 v

28. A vulcanized rubber product resulting from the process as set forth in claim 13.

29. A vulcanized rubber product resulting from the process as set forth in claim 15.

30. A vulcanized rubber product resulting from the processas'set forth in claim 16. i

31. A vulcanized rubber product resulting from the process as set forth in claim18.

Signed at -Passaic, County of 'Passaic, State of New Jersey, this 28 day of August,

1931. .7 CLYDE COLEMAN.

rubber which comprises vulcanizing rubber containing a vulcanizing agent in the 35 reaction of equi-molecular proportions of mercaptobenzothiazole, formaldehyde, and p-toluidine.

pres v ence of the reaction product formed by the' 106 17. A process of producing vulcanized rubber which comprises vulcanizing rubber containing sulphur in the presence of a compound having the probable generalformula R S OH NH R wherein R represents an aryl group and R represents a benzothiazyl group.

18. A process of producing vulcanized rubber which comprises vulcanizing rubber containing sulphur in the presence of a compound having the probable general formula R S-CH NH-R wherein R represents an aryl group and R represents the benzothiazyl group.

19. A process which comprises adding to rubber prior to actual vulcanization an aryl- 55 aminomethyl arylenethiazyl sulphide.

20. A process which comprises adding to rubber prior to actual vulcanization an arylaminomethyl benzothiazyl sulphide.

21. A process which comprises adding to so rubber prior to actual vulcanization a V phenylaminomethyl benzothiazyl sulphide.

22. A vulcanized rubber product resulting from the process as set forth in claim 1.

23.. A vulcanized rubber product resulting 65 from the process as set forth in claim 7.

v .195 v I 

